The present invention generally relates to water heaters and, more particularly, is concerned with a device for controlling the flow of gas to the heater thermostat.
Water heaters usually have a cold water inlet pipe, a hot water outlet pipe and an exhaust or vent pipe all connected to the top of a reservoir or tank. Most water heaters currently utilize natural gas to heat the water within the tank. A heater thermostat attached to the tank controls the flow of gas to a main burner which is usually below the tank. A pilot line for igniting the main burner is also attached to the heater thermostat. After the water within the tank is heated it rises from the bottom to the top of the tank by convection.
Control devices for water heaters have been designed for many purposes such as controlling the water temperature in the top portion of the tank during frequent withdrawals of water from the tank. A control device may prevent the temperature in the top portion of the tank from approaching an unsafe limit or may assure complete shutdown of gas flow to the main burner when the water temperature excessively rises due to the failure of the heater thermostat. Additionally, the control device may regulate the thermostat temperature as a function of water usage or may direct the supply of water to a low temperature area.
If water is not withdrawn from the tank for a long period of time such as when no one is home, the water temperature eventually drops to a value such that the heater thermostat will activate the main burner to heat the water to the proper temperature. This reheating of water is an unnecessary waste of energy and may be avoided by lowering the temperature limit of the heater thermostat. However, this will cause the temperature of the water withdrawn from the tank during actual use to be undesirably low. Alternatively, a control device which changes the thermostat temperature as a function of usage could be used. However, as with most variable control devices it is complex and expensive. Therefore, a device which would cut off the gas flow to the heater thermostat during periods of nonuse could provide a simple and inexpensive solution to the problem. Thus, there is current need for a device which would terminate the transmission of gas to the heater thermostat during periods of nonuse.